Our future is being threatened by exhaustion of fossil fuel resources, increasing cost pressure of energy due to reduced production and cost advancing pressure from oil-producing countries, and serious environmental pollution coming out from energy consumption.
In addition, conventional power generation system using fossil fuels, there are various power generation systems using various kinds of energy resources such as nuclear energy, tidal energy, water energy, wave energy, solar energy, bio energy, and so on.
However, nuclear energy even having economic feasibility has been restrictively developed only in some countries due to the Nuclear Nonproliferation Treaty and radioactive contamination, meanwhile water energy and tidal energy require proper site location satisfying system requirements, anticipated excessive investment and long-term construction period, while solar energy and wave energy require storage cell due to intermittent generation and higher cost.
Accordingly, development of wave power generation system using clean energy is still needed.
Considering those systems consuming fossil fuels, future-oriented new power generation systems using clean energy resources must be competitive in construction costs and operation cost to the conventional electric power systems including land occupations, anticipative investments, construction periods, social costs from environmental pollution, and so on. In addition, the wave power generation system must have high annual operation rate and be free from expensive storage equipment or auxiliary power generation.
Meanwhile, since water having heavier mass has higher kinetic energy than air having lighter mass, the technology converting kinetic energy of moving seawater, i.e., research of generating electricity from wave power, is now in the process.
In particular, considering that most countries have long coastal lines faced to ocean, energy resources from sea wave are out of count. However, frequency and wave power in near shore and offshore have high fluctuations according to environment of the locations and seasons, whereas relatively lower wave height often occurs according to season's weather condition.
Accordingly, if the disadvantage of practice caused by lower wave height and uneven wave period could be overcome, uncountable wave power will be secured at no cost.
Technologies of converting wave power into energy have been opened already as an oscillating water column type, a movable body type, a raft conversion type, a shoulder cam type, an energy amplification and concentration type, wave overtopping type, etc.
The oscillating water column type is most commonly used, but has a number of drawbacks. For example, the oscillating water column type takes long time to construct a large-scale bottom structure and uses inefficient air turbine, leading to cost ineffectiveness and necessarily changing output power due to a change in air pressure. In the case of the raft conversion type, an oil pressure pump with relatively short strokes is cost-ineffective and considered unsafe, so that it garners less interest. Both the oscillating water column type and the raft conversion type are available to generate power only when a wave height reaches a certain level. In addition, both of them are not efficient in energy conversion, and are adapted in a small range of usable wave.
As a raft is the most adequate medium to convert wave energy into useful energy, using mass movement of the raft, so that the raft conversion type may be the most promising method to generate power using wave energy. However, there are still many issues blocking the development of the raft conversion type, including low efficiency of the conversion type, fluctuation of seasonal output power, concerns over stability against an abnormal wave and a gap in expenses between wave power generation and fossil-fuel power generation. Therefore, more researches and development need to be done to address the above troubling problems.
It is true that a wave power generator is superior to other power generators, but, if the wave power generator has a complex structure, for example, requiring a great number of raft vessels and a complicated way of connecting the raft vessels to each other, it may not be cost-effective. For this reason, a new wave power generator, which has a simple structure leading to high energy conversion efficiency and is able to be installed in anywhere, is needed.